1. Field of the Invention
This invention relates to the phase-matching of telescopes in an array fed by a common coherent source and especially to the phase-matching of such telescopes by means of a corner-cube-bridge metering rod.
2. Description of the Prior Art
The high-energy laser (HEL) has great potential as a weapon system due to its ability to deliver large quantities of energy concentrated on a small area at great distances over precisely predictable trajectories at the speed of light. The intensity at the target is proportioned to (DP/.lambda.R).sup.2 where D is the transmitter aperture diameter, .lambda. is the radiation wavelength, P is the transmitted power, and R is the range. The transmitter telescope diameter D is limited by fabrication technology and other practical considerations. A number (N) of telescopes each of diameter (d) and power (p) may be used in an array, but the intensity at the target is only proportional to N(dp/.lambda.R).sup.2. However, if the radiation through the (N) telescopes can be brought into phase on the target, the intensity increases to N.sup.2 (dp/.lambda.R).sup.2. This requires precise path-length equality on all optical paths from a common coherent laser source through each of the separate telescopes to the target. The present invention provides means for measuring path length differences between the telescopes in an array and eliminating the differences.
Similar considerations apply to an array of telescopes observing light from a remote source. Path-length differences through the telescopes affect intensity and resolution in the common focal plane in much the same way.
The common coherent source mentioned above may be laser beams transmitted outwardly through the array of telescopes to a common remote target or a distance source, such as a star, whose light is received by the array and brought to a common focal point.